What we know about the experimental Covid-19 treatment Trump received

President Donald Trump has received an unproven antibody treatment for Covid-19 following a test confirming that he was infected with the SARS-CoV-2 virus, White House physician Sean Conley said in a letter Friday afternoon.

The treatment was developed by the biotech company Regeneron. “Following PCR confirmation of the president’s diagnosis, as a precautionary measure he received a single 8 gram dose of Regeneron’s polyclonal antibody cocktail,” Conley wrote.

(Science reporter Jon Cohen later confirmed with Regeneron that Trump was given a monoclonal antibody cocktail, not a polyclonal cocktail.)

Later in the day, Trump flew to Walter Reed Medical Center, just outside Washington, DC, where officials say he will stay for a few days. “Out of an abundance of caution, and at the recommendation of his physician and medical experts, the President will be working from the presidential offices at Walter Reed for the next few days,” press secretary Kayleigh McEnany said.

There is currently no treatment approved by the Food and Drug Administration to treat Covid-19, though the agency has granted emergency use authorizations to the antiviral drug remdesivir and to convalescent plasma. However, the Regeneron therapy was given to Trump under compassionate use guidelines, which are considered on a case-by-case basis.

Regeneron’s antibody-based treatment, called REGN-COV2, is classified as experimental and is still in clinical trials. The company reported in a September 29 press release that the drug improved symptoms and reduced the viral load in Covid-19 patients who were not hospitalized.

“The greatest treatment benefit was in patients who had not mounted their own effective immune response, suggesting that REGN-COV2 could provide a therapeutic substitute for the naturally-occurring immune response,” said George D. Yancopoulos, president and chief scientific officer of Regeneron, in a statement.

In March, Christos Kyratsous, vice president for infectious disease research and viral vector technologies at Regeneron, told Vox that this treatment could also be used prophylactically to prevent infection, in addition to being used as a treatment for an ongoing infection.

Antibodies are proteins produced by the immune system’s B cells that attach to a pathogen like a virus or to an infected cell. By attaching, they can either inhibit the target from doing damage or flag the target for destruction by other immune cells.

According to Cohen of Science:

One antibody comes from a human who had recovered from a SARS-CoV-2 infection; a B cell that makes the antibody was harvested from the person’s blood and the genes for the immune protein isolated and copied. The other antibody is from a mouse, which was engineered to have a human immune system, that had the spike protein [that helps the virus attach to a receptor on human cells] injected into it.

This type of treatment is a bit different from convalescent plasma, another experimental treatment for Covid-19, which is taken from people who were infected with Covid-19 but recovered. Plasma is the liquid part of blood, including proteins used for clotting, and when harvested from convalescents, it contains antibodies to the virus. So transfusing plasma from someone who recovered to someone who is sick could help them get better, or prevent them from getting sick in the first place.

However, the evidence to support either of these treatments is weak. The National Institutes of Health criticized the FDA’s emergency use authorization for convalescent plasma. “There are insufficient data to recommend either for or against the use of convalescent plasma for the treatment of COVID-19,” the agency wrote in a blunt letter in September.

As for Regeneron’s therapy, the best evidence right now is a press release citing results drawn from an early-stage trial of just 275 people. Without peer review of the findings, or even published data, all we have is the company’s word that this works. “There’s nothing bad about these results, you just can’t say much about how transformative this is going to be,” Eric Topol, director of the Scripps Research Translational Institute, told Stat News.

Some doctors took to Twitter to criticize the decision to administer an experimental drug with limited evidence for its effectiveness to the president of the United States.

Receiving any kind of experimental treatment is a risk, and Trump is at greater risk of a severe course of the disease because of his older age, his obesity, and his gender. And it’s not clear whether the decision to administer the treatment came from Conley or from the president. However, earlier on Friday, Matt McCarthy, an infectious disease doctor, appeared on Fox Business and brought up the idea of using Regeneron’s antibody therapy.

Regeneron CEO Leonard S. Schleifer told the New York Times on Friday that the company received a call from the White House requesting access to the drug. “All we can say is that they asked to be able to use it, and we were happy to oblige,” he said. “When it’s the president of the United States, of course, that gets — obviously — gets our attention.”

The Times also reported that Schleifer knows Trump personally and has been a member of Trump’s golf club in Westchester County in New York.